Method for manufacturing electrodes of a display device utilizing gas discharge

ABSTRACT

Electrodes manufactured by the method according to the present invention are used for generating a firing spot, which is utilized for an indication in a display device utilizing gas discharge or a plasma display panel. First, an electrode pattern having a predetermined dimension is formed in grooves on the inside surface of the dielectric supporting substrate; second, metal paste for electrodes is inlaid in the above-mentioned grooves then, said metal paste inlaid in the grooves is baked, and then the electrodes are formed on the supporting substrate.

United States Patent [1 1 Maeda et al. 1 v

[ 1 Jan.1,l974

[ METHOD FOR MANUFACTURING ELECTRODES OF A DISPLAY DEVICE UTILIZING GAs DIsCIIARGE [75] Inventors: Takashi Maeda; Yasunari Shirouchi,

Akashi, both of Japan [73] Assignee: Fujitsu Limited, Kamikodanake,

Nakahara-ku, Kawasaki-shi, Kanagawa-ken, Japan 221 Filed: July 5,1972

21 Appl. No.: 269,236

[30] Foreign Application Priority Data July 15, 1971 Japan 46/52104 {52] US. Cl 29/624, 29/25.14, 117/213, 117/217, 156/15 [51] Int. Cl. "05k 3/10, HOSk 3/28 [58] Field of Search 29/624, 625; 96/32,

96/362, 316; 117/212, 213, 215, 217; 156/7, 8, 15; 204/29, 30, 32 R, 38 R; l74/68.5; 315/169 R, 169 TV; 313/201, 289, 290, 291

[56] References Cited UNITED STATES PATENTS 3,296,359 l/I967 Ramsey et al. 117/212 X 3,333,334 8/1967 Kuliczkowski et a1 29/625 X 3,573,948 4/1971 Tarnopol 96/362 X Primary ExaminerCharles W. Lanham Assistant Examiner-Joseph A. Walkowski, Jr. Att0rneyNelson E. Kimmelman 57 ABSTRACT Electrodes manufactured by the method according to the present invention are used for generating a firing spot, which is utilized for an indication in a display device utilizing gas discharge or a plasma display panel. First, an electrode pattern having a predetermined dimension is formed in grooves on the inside surface of the dielectric supporting substrate; second, metal paste for electrodes is inlaid in the above-mentioned grooves then, said metal paste inlaid in the grooves is baked, and then the electrodes are formed on the supporting substrate. 1

9 Claims, 4 Drawing Figures 1 METHOD FOR MANUFACTURING ELECTRODES OF A DISPLAY DEVICE UTILIZING GAS DISCHARGE DESCRIPTION OF THE INVENTION The-present invention relates to a method for manufacturing precisely, easily and surely fine metal electrodes used in a display device utilizing gas discharge.

' Generally, in a display device utilizing gaseous discharge, electrodes covered with dielectric layers are positioned opposite each other. Between them is a gap filled with gas capable of ionization. An alternating sustaining signal is applied between the electrodes facing each other, and the firing spots are produced when write pulses larger than the firing voltage are added to the sustaining signal. Wall charges corresponding to the polarity of the applied voltage are then formed. When the potential difference between the wall charges and the following sustaining voltage becomes larger than the firing voltage, the firing spot is again produced, and the polarity of the wall voltage is reversed. Accordingly, once the firing is produced, a sustaining voltage lower than the firing voltage can continuously produce the firing spot. That is, the write information is memorized as the wall voltage and the display can be carried out. Such a gaseous discharge panel has become known in the art as the plasma panel", and when utilized for display purposes is commonly referred to as the plasma display panel.

In the above-mentioned plasma panel, the electrodes covered with dielectric layers are mainly manufactured by methods as shown below:

I. a first method is to apply a transparent electric conductive film on the substrate and finish this film with photo-etching;

2. a second method is to print a metal-paste with screen printing on the substrate;

3. a third method is to vacuum evaporate a coating of metal on the substrate using a predetermined mask.

However, above-mentioned'methods have problems, as shown below: I

In the first method, the resistivity of the electric conductive film is more than lOQ/cm. When this film is formed as a fine electrode having a width of I a, the value of its electric resistance becomes more than I kQ/cm. This distorts the waveform of the driving voltage of the electrode and as a consequence the method is not applicable to the electrodes of a display panel having dimensions larger than 2 inches 3 inches.

In the second method, electrodes ordinarily having a width of 50 I00 p. must be printed for the purposes of increasing the light transparency and to conform to a specification with respect to the firing characteristics. In this case, the thickness of the printed electrodes becomes smaller than 5 a. As a result of this, the abovementioned electrodes are easily broken in the sintering process of the electrodes and in the following, sintering process of the applied dielectric layers. This produces dispersion in the case of manufacturing large size display panels. This is due to the facts that some parts of the metal paste are thickly printed and the other parts thinly printed. The small absolute quantity of the paste causes insufficient adherence of the electrodes on the substrate, and in addition, the thermal expansion coefficients of the electrodes and the dielectric layers are considerably different.

In the third method, it is very difficult to manufacture precisely a large size mask of evaporation coating. Further the vacuum evaporation coating of the metal having a thickness larger than several micron for a large size panel is very expensive and is not applicable to mass production.

An object of the present invention is to provide a method of manufacturing the electrodes of a gaseous display panel which overcomes the above-mentioned drawbacks.

A further object of the present invention is to provide a method of manufacturing the electrodes of a gaseous display panel, in which the pattern of electrodes having widths of 50 u is engraved in grooves having a depth of the order of 5 30 p. on the substrate, the metal paste is coated into the above-mentioned grooves and is baked, whereby a low electric resistance and a uniform electric potential distribution in the electrodes is obtained.

Further features and advantages of the present invention will be apparent from the ensuing description with reference to the accompanying drawings; to which, however, the scope of the invention is in no way limited.

FIG. 1 is a squint view illustrating the construction of a typical display panel utilizing a gas discharge;

FIG. 2 is a sectional view illustrating the construction of a typical display panel utilizing a gas discharge shown in FIG. 1;

FIG. 3 is a schematic illustration of a supporting substrate of electrodes manufactured according to the method of the present invention;

FIG. 4 is a sectionally enlarged view of the supporting substrate of electrodes shown in FIG. 3.

Referring to FIG. 1, a display device utilizing a gaseous discharge 1 has a pair of supporting substrates of electrodes 2 and 2a. The supporting substrate 2 includes a group of electrodes 3 arranged in columns, which are parallel to a vertical axis; dielectric layer 4 covers the group of electrodes 3. The supporting substrate 2a provides a group of electrodes 3a arranged in rows, which is parallel to a horizontal axis; dielectric layer 4a covers the group of electrodes 3a. The supporting substrates of electrodes 2 and 2a are positioned in spaced parallel relation to the groups of electrodes 3 and 3a respectively. As shown in FIG. 2 these parallel rows and columns are separated from each other by a gap 5. This gap 5 is filled with a rare gas having suitable pressure and capable of ionization. When the device 1 is utilized for display purposes, it is necessary that, at least, one of the substrates 2, 2a and one of the dielectric layers 4, 4a are transparent.

In the above-mentioned display device 1 shown in FIGS. 1 and 2, when an electric voltage higher than the firing voltage V, is selectively applied between the groups of electrodes in columns 3 and rows 3a, each cross point of the electrodes in columns and row discharges into the gap 5 filled with an ionizable gas. At the time of this discharge, a wall charge is formed near the above-mentioned cross point in the dielectric layers 4 and 4a. With the effect of this wall charge, the discharge which is once generated is sustained if the pulse sustaining voltage V, is smaller than the firing voltage V, and is continued. That is, the information which inputs as .the voltage exceeding the firing voltage V, is kept in memory by the above-mentioned wall charge.

The above-mentioned discharge is carried out at a discharge point for display.

Except for the basic construction shown in FIGS. 1 and 2 various constructions may be used for the display device utilizing gas discharge. For example, a device having cell spacers in the gap filled with a gas or a plate discharge type device which arranges the group of electrodes on the common plane substrate may be used. In the latter case the discharge is produced between the electrodes adjacent each other on the same plane substrate. Self shift type devices having a function of selfshift of the discharge spot, may also be used.

Next, explanation will be given to the method for manufacturing the assembly which forms the electrodes in columns 3 and rows 3a respectively, and the dielectric layers 4 and 4a respectively, on the supporting substrates of electrodes 2 and 2a respectively, of the display device utilizing gas discharge.

FIG. 3 is a plan view of the supporting substrate of the present invention and FIG. 4 is a sectional view of the supporting substrate of electrodes shown in FIG. 3. First, the supporting substrate 6 having the dimension of 440 X 380 X 10 mm is cleaned with chromic acid mixture and then washed with pure water and dried. Next, a photo-sensitive resin of synthetic rubber groups is coated on the substrate 6. Then, the pattern of electrodes having a width of 50 p. is exposed onto the substrate, and the substrate is developed. The developed pattern is then etched about two minutes with an etchant composed of 46 percent solution of hydrofluoric acid, 12% normal solution by hydrochloric acid and water. The ratio of weight of these components is 100 3 20. As a result of this, etched grooves with depth about 12 p. are formed on the substrate. These grooves are coated with gold paste for low temperature baking and the substrate is baked. As a result of this, the fine electrodes 7 are adhered to the substrate under the best conditions without causing disconnections. For the purpose of forming the dielectric layers 8 on the upper layer of the electrodes as shown in FIG. 4., solder glass ofa lead oxide-boric acid group is coated over the electrodes. This coating is then treated about thirty minutes with heat at 520C, and a flat dielectric layer 8 is obtained. During the treating process, neither diffusion nor disconnection are caused with respect to the fine electrodes. The practical display panel provides two supporting substrates of electrodes which are positioned in spaced parallel relation having their inside surfaces opposite each other and separated by a gap filled with gas capable of ionization. In some types of display panels, the discharge is produced between electrodes adjacent to each other on the same substrate on which a gap filled gas capable of ionization is provided.

In the above example, gold paste was used for adhering the electrodes to the substrate, however, other pastes, having for example, silver, platinum or salladium as a main component can be applicable with similar effects. Generally, metal pastes which include precious metals as a main component are applicable for the above-mentioned object. However, sufficient result can not be obtained with a paste which includes rhodium.

With respect to the method of forming the fine grooves, the same result is obtained with a sandblast process and ultrasonic work.

As is clear from the above explanation, this method for manufacturing the electrodes provides many advantages. Some of these are pointed out below.

a. Warp of the supporting substrate of electrodes can be considerably decreased. When tin oxide is used as electrodes, considerable warp is caused when forming the thin film of tin oxide. For example, when a span having a dimension of 35 cm is used, the warp of span becomes 50 300 ,u. According to the method of the present invention, the warp is within :30 pt when a span having a dimension of 35 cm is used.

b. The thickness of the electrode layer is adjustable and, therefore, the electric resistance of the electrode layer can be selectively determined.

c. In the case of electrodes with the same width, the method of the present invention can provide a larger adhesive area of the electrodes to the supporting substrate than other methods. The adherent strength therefore, becomes larger than other methods.

d. Diffusion in width of electrodes during the baking process of the covering dielectric layer does not result because the electrodes are buried in the supporting substrate.

e. A dispersion in the widths of the electrodes is also not produced.

f. The manufacturing process is simple and is suited to a mass production.

What we claim is:

l. A method of manufacturing a plasma display device or the like having at least one dielectric substrate on which an electrode arrangement is to be disposed comprising:

a. the step of forming grooves on one surface of said substrate with a predetermined pattern corresponding to said electrode arrangement;

b. the step of applying conductive metal paste for electrodes in said grooves;

c. the step of baking said one surface; and

d. the step of covering said baked surface with a dielectric layer.

2. A method of manufacturing electrodes ofa plasma display device or the like according to claim 1, wherein said step of forming grooves is carried out by photoetching grooves having a depth of 530[.L.

3. A method of manufacturing electrodes of a plasma display device or the like according to claim I, wherein said metal paste for electrode is composed of a precious metal as a main component.

4. A method of manufacturing a component of a plasma display device or the like having at least one dielectric substrate comprising:

a. forming a predetermined pattern ofgrooves on one surface of said substrate by photo-etching,

b. applying conductive paste having a precious metal as a main component in said grooves,

c. baking said grooved surface at a relatively low temperature thereby to adhere said precious metal to said grooves, and

d. coating said baked grooved surface with a dielectric layer.

5. A method according to claim 4 with the addition of the step of subjecting said coated substrate to a temperature substantially higher than said relatively low temperature.

6. The method according to claim 5 wherein said paste of conductive metal is a precious metal from the following group: gold, silver, platinum, or palladium.

grooves have widths on the order 50-100 microns.

9. The method according to claim 6 wherein said baked-on metal in said grooves has a thin depth on the order of 5-30 microns. 

1. A method of manufacturing a plasma display device or the like having at least one dielectric substrate on which an electrode arrangement is to be disposed comprising: a. the step of forming grooves on one surface of said substrate with a predetermined pattern corresponding to said electrode arrangement; b. the step of applying conductive metal paste for electrodes in said grooves; c. the step of baking said one surface; and d. the step of covering said baked surface with a dielectric layer.
 2. A method of manufacturing electrodes of a plasma display device or the like according to claim 1, wherein said step of forming grooves is carried out by photo-etching grooves having a depth of 5-30 Mu .
 3. A method of manufacturing electrodes of a plasma display device or the like according to claim 1, wherein said metal paste for electrode is composed of a precious metal as a main component.
 4. A method of manufacturing a component of a plasma display device or the like having at least one dielectric substrate comprising: a. forming a predetermined pattern of grooves on one surface of said substrate by photo-etching, b. applying conductive paste having a precious metal as a main component in said grooves, c. baking said grooved surface at a relatively low temperature thereby to adhere said precious metal to said grooves, and d. coating said baked grooved surface with a dielectric layer.
 5. A method according to claim 4 with the addition of the step of subjecting said coated substrate to a temperature substantially higher than said relatively low temperature.
 6. The method according to claim 5 wherein said paste of conductive metal is a precious metal from the following group: gold, silver, platinum, or palladium.
 7. The method according to claim 6 wherein said (a) step is preceded by cleaning said one surface of said substrate with a chromic acid mixture which is then washed off with water and said one surface is dried.
 8. The method according to claim 4 wherein said grooves have widths on the order 50-100 microns.
 9. The method according to claim 6 wherein said baked-on metal in said grooves has a thin depth on the order of 5-30 microns. 